What’s the future of geo-location for me?

I can’t quite see where geo-location is going.  I know that every programmer and marketer worth their weight is working to figure out out how to track our whereabouts and make it useful to the world at large.  The question is, where can it be constructive and useful to us as people and consumers and where does it invade privacy?  I may want to receive an instant coupon for the phenomenal homemade ice cream shop as I pull into town and park my car nearby (maybe I’ll just treat myself and my wallet today), but I don’t think I really want Marcy Wendell, from 7th grade, to find me at my 25th college reunion dinner in Soho, do I?  With the new geo-location technology, will we have any control over when it’s tracking us and when it’s not?  And will the average mobile device user know how to manipulate it’s on/off switch?